Motor control apparatus



April 22, 5 w. R. WICKERHAM 2,832,024

MOTOR CONTROL APPARATUS Filed July 11, 1955 '7 Sheets-Sheet 1 INDUCTOR UNIT M Lower I 'Hoist' 3 2 l O l 2 3 CONTROL umr ALB INVENTOR WITNESSES Fig.

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MOTOR CONTROL APPARATUS Filed July 11, 1955 7 Sheets-Sheet 2 April 22, 1958 w. R. WICKERHAM MOTOR CONTROL APPARATUS 7 Sheets-Sheet 3 Filed July 11, 1955 m C U D N I I AMPLIFIER UNIT l I l I CONTROL UNIT April 1958 w. R. WICKERHAM 2,832,024

MOTOR CONTROL APPARATUS Filed July 11, 1955 7 Sheets-Sheet 4 Fig. 2B.

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' MOTOR CONTROL APPARATUS Filed July 11, 1955 '7 Sheets-Sheet 5 INDUCTOR UNiT L2 52 so| l [RBI VERNlER UNIT 3" 32l CONTROL UNIT 'Lower Hois t April 22, 1958 w. R. WICKERHAM MOTOR CONTROL APPARATUS 7 Sheets-Sheet 6 Filed July 11, 1955 Fig'. 3B.

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MOTOR CONTROL APPARATUS A ril 22, 1958 Filed July 11, 1955- 7 Sheets-Sheet 7 Fig.4

Terminals to I82 Terminals to [SI 0 Off Position of Vernier Rotor in Mechanical Degrees United States Patent MOTOR CONTROL APPARATUS William R. Wickerham, Buffalo, N. Y., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 11, 1955, Serial No. 521,104

9 Claims. (Cl. 318-202) I This invention relates to motor control apparatus and has particular relation to motor control apparatus for controlling hoist motors, such as are used in the operation of cranes. This application is a continuation-inpart of application Serial No. 277,749, filed March 21, 1952, now Patent No. 2,774,923, and entitled Electric Control for Alternating-Current Motor (herein called parent application). This application also relates to an application Serial No. 521,076, filed July 11, 1955, to Wellington C. Carl and E. C. Rhyne, for Motor Control Apparatus, filed concurrently herewith. Both the parent application and the Carl et al. application are assigned to Westinghouse Electric Corporation and both are incorporated in this application by reference.

Hoist motors are usually of the three-phase induction type and are supplied from a commercial threephase source. Such motors drive a so-called hook to which the load may be attached. It is customary to refer to the load on the hook in describing the load to which the motor is subjected. In operating hoists or cranes, it is desirable that the motor driving the hoist or crane be precisely controllable. Thus, it is essential that when a raising operation is started a high torque be available. At the start of the operation the motor speed should, in addition, be low, so that when there is load on the hook, jerking of the load is avoided and when there is no load on the hook, precipitous raising of the hook is avoided. It is also desirable that the speed and torque be low at the start of a lowering operation, particularly if there is no load on the hook. If there is a load on the hook, it is desirable that the direction in which the motor exerts torque be readily reversible to suppress excessive tendency of the load to overhaul the motor. It is then essential that a full range of controllable torque be available at low lowering speeds. Naturally, it is desirable that this condition be met without supplying excessive currents to the motor.

Apparatus in accordance with the teachings of the at the same time including facilities for providing a full range of controllable torque at all speeds of the hoist prior art is typified by Wickerham Patent 2,440,319. In

this case, the motor (HM, Fig. 1) is supplied through two sets of inductors (A1, A2, B1, B2) which are connected between two of the phase buses (L1, L2) of the supply and two of the terminals (T1, T2) of the motor. The inductors are controlled to unbalance the phase of the potential supplied to the motor and in this manner to control the speed and the direction of rotation of the motor. The apparatus disclosed in this patent has been found to operate reasonably satisfactorily but it has the disadvantage of complexity, in that it requiresat least four inductors, each of which draws load current and absorbs a portion of thepotential available from the supply. In addition, the control is complicated, including two sets of variable resistors (CA and CB) one associated with inductors A1 and A2 and the other with inductors B1 and B2. q It is, accordingly, broadly an object of this invention to provide a hoist drive of relatively simple structure involving relatively simple operating requirements and motor, and particularly at low lowering speeds, and affording high precision in load handling.

A hoist drive of simple structure is disclosed in the parent application. In thisdrive the motor is supplied with power from a so-called duplex interconnected threephase system. Such a supply consists essentially of two delta connected three-phase supplies having in common two of their supply conductors (L1-L3, Fig. 1, parent), the third conductors (L274, Fig. l) of each supply being at opposite phase potentials. Instead of the four inductors of Patent 2,440,319, the drive disclosed in the parent application includes only a pair of inductors (MR and BR) which are connected in series between the op-' posite phase conductors of the two supplies. Two of the terminals of the motor are connected to the common conductors and the third to the junction of the inductors. In the apparatus disclosed in the parentapplication the inductors are controlled from three principal control components which supply three potentials, a potential (R4, Fig. 1) responsive to the load on the motor, that is, to the weight being lowered or lifted, a potential (PG) responsive to the speed of the motor and a vernier potential (VS) which is set to achieve the speed best suited to each operation. In accordance with the teaching of this parent application the three potentials areimpressed in series.

The apparatus disclosed in the parent application has, on the whole, been found to operate satisfactorily, but

, its operation has not been as precise as is desirable for many of the hoist problems encountered. In addition,

the structure of the apparatus disclosed in the parent ap-' plication is still relatively complex.

It is, accordingly, specifically an object of this invention to provide apparatus of the general type disclosed in the parent application which shall be more precisely controllable than the apparatus disclosed in the parent application. I

It is another object of this invention to provide apparatus of relatively simple structure for controlling the speed and torque of a motor, particularly a hoist motor, which, in spite of the simplicity of its structure, shall afford the operator facilities for achieving the most propitious speed and torque for each condition under which i the motor is operated.

It is an incidental object of this invention to provide a novel inductor circuit.

This invention arises from the realization that the con- .nection of the vernierpotential in series with the weight responsive and speed responsive potentials in the drive disclosed in the parentapplication' reduces the precision of the apparatus disclosed in the parent application. It has been discovered that this reduction in precision arises from the fact that when the three potentials are impressed In accordance with a further aspect of this invention, a

, vernier potential source isprovided which supplies two operator the facility for setting the motor to produce any Patented Apr. 22, 1958 speed and torque desired within narrow limits. The vernier components in this case are, in one embodiment of this invention, supplied through a pair of magnetic amplifiers, and in a modification of this invention, supplied from the outputs of an inductor unit.

Still another aspect of this invention is specifically tied up with the control of the rotor resistance of the motor in the later stages of a hoisting operation. In accordance with the usual practice, resistances are connected in the rotor circuit of the motor and during the later stages of a hoisting operation these resistances are, inpart or in whole, shunted out. In accordance with a specific aspect of this invention, the contactor which shunts out the resistors during a late stage of the operation also shunts out the hoist (or up) inductor, the impedance of which is reduced when the motor is to have a hoisting torque. In this way, a highly desirable feature of operation is achieved in a simple manner by operation of a single contactor.

The apparatus including the above-described features has been found to operate precisely and to lend itself to precise control of speed and torque over a wide range. To demonstrate how precisely this apparatus operates, an ordinary walnut wasplaced adjacent to a watch on a block directly under a weight driven by the hoist motor controlled in accordance with this invention. It was found possible to control the lowering of the weight so precisely that it cracked the walnut Without touching the watch.

The novel features considered characteristic of this invention are disclosed generally above. This invention, both as to its organization and its method of operation together with additional objects and advantages thereof, will be understood from the following description of specific embodiments read in connection with the accompanying drawings, in which:

Figures 1A and 1B constitute a circuit diagram of one embodiment of this invention;

Figs. 2A and 2B constitute a circuit diagram of a modification of this invention;

Figs. 3A and 3B constitute a circuit diagram of a further embodiment of this invention; and

Fig. 4 is a graph illustrating the operation of a Vernier in accordance with this invention.

DescriptinFigs. 1 A-JB The apparatus shown in Figs. 1A and 18 includes a Motor, 2. Hoist, an Inductor Unit and a Control Unit. This apparatus is supplied from the conductors L1, L2 and L3, which may be the phase conductors of a commercial three-phase supply and the conductor L4, which derives its power through the secondary 181 of transformer 12. The conductors L1, L2, L3 and L4 constitute a duplex interconnected three-phase source. For control purposes, there are, in addition, the conductors ALI and AL2 which derive their power from the secondary 1820f the transformer 12, and the conductors AL3 and AL4 which derive their power from the secondary 183.

The Motor includes a field winding having terminals T1, T2, T3 and a rotor preferably of the wound type having terminals RT1, RT2, RT3. The rotor terminals RT1, RT2, RT3 are interconnected by pairs of resistors 11,13, 15, 17, 19, 21, one set 11, 15, 19 of which may be shunted out by the contacts .23 and 25 of relay RESI and the other set 13, 17, 21 by the contacts 27 and 29 of. relay RES2. Relays RESI and RES2 are in the Control Unit. The Motor also includes a brake B which may be released by operation of 'a solenoid SB. Further, the Motor includes a limit switch mechanism including the limit switch LS which is opened when the Hoist reaches its upper limit.

The Hoist is of the type disclosed in the parent application. It includes a hoist drum DR which is connected to a hook HO through a cable C, a pair of sheaves SH! and 81-12 and an equalizer sheave SHE. The drum DR is rotatable by the Motor and drives a tachometer T which has a field winding TS and produces apotential proportional to the speed of the drum DR. The field winding TS derives its power from the conductors AL3 and AL4 through a rectifier RF supplied from a transformer 1AZ. The Hoist is connected through the equalizer sheave SHE to a weight inductor WI in the manner disclosed in the above-identified parent application and in an article on page 5 6 of Westinghouse Engineer for March 1952. The secondary of the inductor WI is connected to a rectifier RW which supplies a potential proportional to the load on the hook.

The Inductor Unit includes a pair of inductors Id and In. Inductor Id has output windings 31, a bias winding 33 and an input winding 35. The inductor It! has output windings 41 and an input winding 45. The inductors id and It: are of the saturable type, the saturation being determined by the magnitude of the current through the biasing Winding 33 and the input windings 35 and 45 and the impedance of the inductors Id and In depending on the magnitude of the saturation. Such inductors are available in the art with additional windings for biasing or other purposes. The use of inductors, including such additional windings, are within the scope of this invention, but for the purpose of this invention it is only essential that the inductors have the windings above mentioned.

The output windings of inductors Id and In are connected through the contacts 51 and 53 of a contactor M in series between conductors L2 and L4 which are at opposite phase potentials. The junction J of these output windings is connected to the terminal T2 of the motor. The terminals T1 and T3 of the motor are respectively connected to the conductors L1 and L3 through additional contacts 55 and 57 of the contactor M. With the Motor so connected, its lowering torque increases as the impedance of inductor Id is reduced and its hoisting torque increases as the impedance of In is reduced.

The Control Unit controls the supply of current to the input windings 35 and 45 of the inductors Id and In and also the operation of the Motor and the resistance in its rotor circuit. Among the principal components included in the Control Unit are a rectifier RB for supplying the bias to the inductor Id, a Vernier unit V, a rectifier RH for supplying current to the input winding 45 of inductor Iu when the hoisting torque of the motor is to be boosted, the rectifier RW and a rectifier RBR for supplying the braking solenoid SB. In addition, there are the main line contactor M, the time delay relay RETI through which the contactor M is locked in once the operation is started, the relay REB controlling the braking solenoid SB and the current for the winding TS, and the already mentioned relays RESl, RES2 and RET2. The interconnection of the above-mentioned control components with the Inductor Unit and the Motor is controlled by .a master switch MS which has three hoist positions labeled 1, 2, 3, three lower positions labeled 1, 2, 3, and a centralstandby position labeled 0. The relay RETl is of the type that pulls in immediately on energization and drops out on deenergization after a time delay. Thus the master switch MS can be moved from Hoist to Lower through ,0 or vice versa while the relay RETl remains actuated.

The rectifier RB is supplied from the conductors ALI and AL2 through .a contact 61 of the switch MS and a variable resistorRIV which controls the magnitude of the bias. With the switch MS set in the 0 position, in lower position 1, or in any hoistposition, the maximum resistance from the variable resistor RIV is connected in series with the rectifier RB. With the switch in lower position 2 this resistance is reduced to a predetermined magnitude, with the-switch in lower position 3, the resistance is further reduced. The rectifier RB supplies current to the bias winding of the inductor Id to reduce its impedance. This current is supplied with the apparatus in standby condition. Thus, in this condition the impedance of the inductor Id is'reduced by the bias winding so that in the absence of current through the input winding 45 of the inductor Iu or through the input winding 35 of inductor Id, the potential which would be supplied to the Motor if the contactor M were closed is such as to cause the Motor to produce a down torque.

The vernier V includes a vernier inductor VI and a. rectifier RV. The vernier inductor V1 is similar to an induction regulator and may be made up from a stand-- ard repulsion start induction runmotor differing from such a motor in which the commutator and brush rigging are omitted. The rotor may be provided with a handle for setting the inductor VI. The stator windings of the inductor are supplied from the conductors AL3 and AL4. The rotor windings supply the rectifier RV. The rectifier RV is connected to contacts 63 and 65 of switch MS to supply the input windings 35 and 45 of the inductors Id and In in position 0, hoist position 1 and any lower position in a circuit extending from the positive terminal of the rectifier RV, the contact 63 of the switch MS, the input winding 35, the other contact 65 of the switch MS, the rectifier RH, the input winding 45 to the negative terminal of the rectifier. This is an independent circuit including substantially only the vernier supply. When the rectifier RV is energized current is thus supplied to the input windings from the vernier rectifier RV. The current thus supplied to the input winding 35 of the inductor Id is such as to counteract the current supplied through the bias winding and reduce the down torque. The effect of the current through the input winding 45 of inductor In is such as to decrease the impedance of the inductor In and increase the up torque. The displacement of the handle on the rotor of inductor VI in either direction increases the current supplied by the rectifier RV. Thus, the efiect of any displacement is to increase the up torque and decrease the down torque.

The hoist boosting rectifier RH is adapted to be supplied from the conductors ALI and AL2 through a contact 67 of the switch MS and a variable resistor RZV in hoist positions 1, 2, 3. In hoist position 1 the resistor R2V is at a maximum and in positions 2 and 3 the resistance R2V is reduced. In 0 position, any lower position or hoist position 1, the rectifier RW, the tachometer T and the rectifier RH are connected in a circuit with the input windings which is separate from that of the vernier V and which extends from the positive terminal of the rectifier RW through the tachometer T, the input.

winding 35 of inductor Id, the contact 65 of switch MS, the rectifier RH, the input winding 45 of inductor Iu, a part of conductor AL3 to the negative terminal of rectifier RW. In this circuit the rectifier RH does not supply current unless it is energized, that is, unless the master switch is in hoist positions 1, 2 or 3. The current which is supplied when the master switch is in positions 1, 2 and 3 decreases the impedance of the inductor It! and increases the impedance of inductor Id, thus increasing the up torque of the motor and decreasing its down torque. In the preferred practice of this invention the potential supplied by the tachometer T is small compared to the potential supplied by the weight rectifier RW. The potential of the weight rectifier RW is such as to decrease the impedance of the inductor Iu, that is, increase the up torque and increase the impedance of the inductor Id, that is, decrease the down torque. The potential ap plied by the tachometer T enhances or reduces the potential supplied by the rectifier RW depending on the direction of rotation of the hoist drum. When the rotation is in the lowering direction the potential supplied by the rectifier RW is enhanced, that is, the up torque is increased and the down torque decreased, and when the direction of rotation of the Motor is in the raising direction the output of the rectifier RW-is reduced by the tachometer T, that is, the up torque is reduced. Thus, the tachometer T functions to reduce the speed of the load regardless of the direction in which it is moving.

. In hoist positions 2 and.3 the rectifier. RH is connect-- 76 ed directly to the input winding 45. In hoist positions 1, 2, 3 and lower position 1 and 2 the coil of contactor M is adapted to be connected in a circuit extending from conductor AL3 through the limit switch LS, load limit switch LK, contacts 69 or 71 of the master switch MS, the coil of -contactor M to conductor AL4. The coil of contactor M is also adapted to'be connected in a circuit extending from conductor AL3 through the limit tains the cont-actor M actuated in lower position 3. This connection prevents the power supply to the Motor from being interrupted for a predetermined time interval after the brake is applied when the switch MS is set to deenergize the Motor. Also when the master switch MS is moved through 0 from Hoist to Lower or vice versa, relay RETI prevents contactor M from dropping out.

Stand-byFigs. 1 A] B In the stand-by condition of the apparatus, the conductors L1, L2, L3 are energized from the commercial supply through the usual disconnects or circuit breakers (not shown. Since conductors L1 and L2 are energized, transformer 11 is supplied with potential and conductor L4 is energized. Conductors ALI, AL2, AL3, and AL4 are also energized. i

In the stand-by condition, the switch MS is at the 0 setting. In this setting the rectifier RB is energized and bias is supplied to the inductor Id which reduces its impedance. The hoist boosting rectifier RH is deenergized. The rectifier RV isenergized and is connected to the input windings 35 and 45 of the inductors Id and Ia and supplies potential to these input windings which would tend to increase the impedance of inductor Id and decrease the impedance of inductor Iu. The vernier RV may be initially set so as to produce the desired initial torque. Usually this setting is made on the assumption that there will be initially no load on the hook, and under such circumstances, the vernier inductor VI is set to produce 30 to 50% down torque.

The weight responsive rectifier RW and the tachometer T are connected in a circuit with the input windings 35 and 45 ofthe inductors Id and la through the contact 65. Withjthe Motor at rest the tachometer potential T is zero. With no load on the hook HO the output of the rectifier RW is substantially zero and substantially no current flows in this circuit. With load on the hook the potential output of the rectifier RW is substantial, depending on the load and current flows in this circuit. This current is of such polarity as to tend to increase the impedance of inductor Id and decrease the impedance of inductor Iu.

Relay RETl is deenergized, as is also contactor M. The contacts of contactor M are then open and conductors L1, L2, L3 and L4 are disconnected from the output windings of the inductors Id and Iu. In addition, at another normally open contact 81 of contactor M and at the switch MS the circuit through the coil of the braking relay REB is open. At the switch MS the circuits through the exciting coils of the relays RESI, RES2 and RET2 are open so that these relays are deenergized and full resistance 11 through 21 is connected in the rotor circuit.

OperationFigs.1A-1B In describing the operation, it will first be assumed that there is no load on the hook H and that it is desired to lower the hook. Under such circumstances, the switch MS is moved to lower position 1. In this position the circuit through the exciting coil of -the contactor .M is closed at contact 69. .Contactor M is then actuated and "at its main contacts connects the inductors Id and In to the conductors L1, L2, L3 and L4. In addition, with the switch MS in lower position '1, a circuit is closed through the exciting coil of relay REB through the contact 83 of switch MS and the contact 81. Trans-former 1AZ is then energized from conductors AL3 and AL i, the circuit is closed through rectifier RBR and the solenoid SB is energized, releasing brake B. In addition, the resistance in circuit with the supply to rectifier RBR is increased by the opening of a contact 85 of solenoid SB. Further, rectifier RF is energized and current is supplied to the field TS of the tachometer T. Current is also supplied to the exciting coil of relay RETl through the contact 69 of the switch MS and relay RETE is actuated at .once, closing a lock-in circuit through con tact 73 for the contactor M which permits contactor M to remain energized in lower position 3 of the switch MS and after the switch MS is reverted to its standby position. This prevents the deenergization of the Motor before the brake B is reengaged, so that when the cleenergization of the Motor starts, electrical (torque) braking as well as mechanical braking is applied.

The output windings of the inductors id and In are now connected in circuit with the motor. At this time, the rectifiers RB and RV are supplying current to the input windings 33, 35 and 45 of the inductors Id and In. Since there is no load on the hook the current supplied by the rectifier RW is substantially zero; the tachometer potential is also zero. As a rule the potential of rectifiers .RB and RV is such that a lowering torque of about 30 to 50% of rated torque is available. The motor then rotates in the lowering direction, lowering the hook. As the motor rotates, potential appears at the terminals of the tachometer T. This potential is of such polarity as to decrease the lowering torque and increase the up torque. The speed of the hook is stabilized at about 30 to 40% rated speed.

If it is desired that the hook HO be lowered at a higher speed, the switch MS maybe moved to lower position 2. In this position a portion of the resistance RlV in circuit with the rectifier RB is shunted out, decreasing the inipedance of the down inductor Id and increasing the down torque. Still higher down speed maybe obtained in lower position 3 where additional resistance in series with the rectifier RB is shunted out and the output of the rectifier further increased. In lower position 3 a circuit is also closed through the exciting coil of relay RETZ by contact 87 of the switch MS. This circuit extends through the contact 73 of relay RETT, the contacts 69 and '87 of the switch MS, the exciting coil of relay to conductor AL4. After a predetermined time interval, relay RETZ is actuated, closing a circuit through relay RESZ which shunts out the resistance 11 through 21 in e the rotor circuit of the Motor. The Motor is thus, at this point, driven in the lowering direction at the maximum speed.

Now assume that a load is being lowered. In lower position 1 the rectifier RW now supplies potential dependent upon the ma-gnitude of the load. This potential is of such polarity as to decrease the impedance of the hoist inductor It: and increase the impedance of the lower inductor Id, correspondingly increasing the up torque relative to the down torque. The torque available may thus be adjusted to the load. The inductor VI and the rectifier RV permit vernier changes in the torque so that the highest precision is attainable. Because the rectifier RV is connected in a circuit independently of the load rectifier RW and the tachometer T, the Vernier has the optimum effect and even if its components VI and RV are small it is highly etiective.

The operation in lower positions 2 and 3 is the same with load on the hook HO as with no load on the hook, except that the rectifier RW governs the magnitude and polarity of the :speed and torque supplied by the Motor: If the load is very heavy and would tend to overhaul the motor at a high speed, the effect of the rectifier RW is to produce a net up torque in the Motor. The magnitude of this net up torque may be precisely controlled by the Vernier VI. As is explained in the parent application, an excessive load would open the load limit contact LK and this would cause the contactor M to be deenergized. The brake would then be applied to the Motor and the Motor while braked would tend to coast to zero speed. Under such circumstances, the dynamic braking effect of the Motor and of the tachometer T would prevent the load from being lowered at too high a speed.

Now assume that there is no load on the hook HO and the hook is to be hoisted. Under such circumstances, the switch MS is moved to hoist position 1. In this position, the potential supplied to rectifier RB is unchanged but the hoist booster rectifier RH is energized through the resistor RZV and the associated contact 67 of the switch MS. The potential supplied by the rectifier RV remains unchanged and the rectifier RW and the tachometer T remain connected as described. The contactor M and the relay RETl are actuated through the contact 71 of switch MS and the relay REB through the contact 91 of switch MS.

Power is then supplied to the Inductor Unit, the brake B is disengaged and power is supplied to the field TS of the tachometer T. At this point, the potential supplied by the rectifier RW and the tachometer T is substantially zero.

The input windings 35 and 45 of the inductors Id and In are now then supplied in the same manner as with the switch MS set for lowering, except that current is supplied by the rectifier RH. This has the effect of increasing the hoisting torque and decreasing the lowering torque to a point at which the hook is hoisted. In this case, the tachometer T supplies a potential tending to reduce the up torque and increase the down torque. The effect of the combination of potentials impressed in this case is such that the hook is hoisted at a speed of 30 to 40% rated speed.

If higher hoisting speeds are desired, the switch MS is moved to hoist positions 2 and 3 in succession. In positions 2 and 3, the resistance R2V in series with the rectifier RH is reduced. In addition, in positions 2 and 3 the rectifiers RV, RW and the tachometer T are disconnected from the input windings of the inductors Id and In and the rectifier RH remains connected only to the input winding 45 of the inductor Ill. The up torque is now substantially increased and the hook moves at a higher speed. In hoist position 3, relay RESI is first actuated through contact 71 of switch MS shunting out a portion of the resistance (11, 15, 19) in the rotor circuit. In addition, relay RETZ is actuated, and after a predetermined time interval, relay RES2 is actuated and the remainder of the resistance (13, 17, 21) in the rotor circuit is shunted out. The book is then raised at the maximum speed.

The operation with weight on the hook is similar, except that in hoist position 1 the output of rectifier RW sets the up torque in dependence upon Weight on the hook and the Vernier VI may then be adjusted to yield precisely the desired up torque.

Description-Figs. 2A-2B The apparatus shown in Figs. 2A and 2B includes a Motor, a Hoist, an Inductor Unit, an Amplifier Unit and a Control Unit. This apparatus is supplied with power from the duplex interconnected three-phase source including the conductors L1, L2, L3 and L4, conductor L4 being supplied from the secondary 53 of transformer 5Z.

The primary 5? of transformer SZ is connected betweenconductors L1 and L3. In addition, potential for the auxiliary components is supplied from the conductors AL5 and AL6 supplied through the transformer 22, the primary 2P of which is connected to the conductors L2 and, L3 sothat the conductors AL5 and AL6 are'energ'ized independently of the position of the contactor 1M which controls the connection of the conductors L1, L2, L3 and L4 to the Motor. Further,'there are the auxiliary conductors'AL7, AL S, AL9, AL10, AL11 and AL12 which are supplied from the secondary 38 of the transformer 3Z through the transformer 2Z. The dilference of potential between the conductor AL7 and the other of these conductors increases progressively as the ordinal following the L increases. An additional conductor is the conductor AL13 which is, in effect, a supply conductor since it is connected to the conductor AL5 through the limit switchesLS and LK. It is believed convenient for the purpose of tracing the circuits to regard AL13 rather than AL5 as a supply conductor.

.The Motor and Hoist are similar to the corresponding components of the apparatus shown in Figs. 1A and 1B.

The Inductor Unit includes the inductors 1Iu and 1.Id. The inductor l-Iu has output windings101 and input windings 103 and 105. The input windings are connected in series across a biasing network B1 which includes a rectifier RBI and a variable resistor 107. The inductor 1Id has output windings 111 and input windings 113 and 115. A biasing network B2 including a rectifier R132 and a variable resistor 117 is connected across one of these input windings 115. The output windings 101 and 111 of the inductors l-Iu and I-Id are connected in series between the conductors L3 and L4 which are at opposite phase potentials through a contact 121 of contactor 1M. The junction I of these output windings is connected to the terminal T3 of the Motor. The terminals T1 and T2 are connected respectively to the conductors L1 and L2 through the remaining contacts 123 and 125 of the contactor 1M. I p

The biasing networks B1 and B2 are energized from the Amplifier Unit. One input terminal of each of the networks is connected to theconductor AL7. The

other terminal of the network B1 is connected to the output conductor L01 of the Amplifier Unit through normally closed contacts 127 and 129 of relays REH and REL. The other terminal of the network B2 issimilarly connected to output conductor L02 of the Amplifier Unit through other normally closed contacts 131and 133 of the same relays. The last mentioned terminal of network B2 is further adapted to be connected through the normally closed contact 133 of relay REH, normally open contact 135 of relay REL and a variable resistor 136 to conductor AL12. The corresponding terminal of network B1 is similarly adapted to be connected through normally closed contact 127 of relay REL, a normally open contact 137 of relay REH and the resistor to conductor AL12. It is seen that when relay REH is actuated the input windings 103 and 105 of amplifier l-Iu are supplied with current independently of the Amplifier Unit which may be substantially higher than the current supplied through the Amplifier Unit and when relay REL is actuated the input winding 115 of amplifier 1-Id is supplied with current independently of the Amplifier Unit which may be substantially higher than the current supplied through the Amplifier Unit but is usually lower than the current supplied to the input winding of the inductor 1Iu.

The Amplifier Unit includes a pair of magnetic amplifiers Au and Ad. Each of these amplifiers has output windings 141 and 151, bias windings 143 and 153 and vernier windings 145 and 155. Each set of output windings has an intermediate terminal which is connected to The bias windings, are supplied in series from arec'tifier RX in a circuit extending from the positive terminal of the rectifier through a voltage divider 161, a variable resistor 163, the bias windings 153 and 143 of the amplifiers Ad and Au to the negative terminal. The vernier windings 145 and 155 are similarly supplied from the rectifier RX in a circuit extending from the positive terminalof the rectifier through another divider 165, a variable resistor RVl, a furthervariable resistor 167,- the vernier windings, still another variable resistor RV2 to the negative terminal of the rectifier. The rectifier is supplied from the conductors AL7 and AL8. The variable resistors RVl and RV2 in circuit with the vernier windings are used to set the vernier current which is supplied through the amplifiers Au and Ad to the input windings, 103 and 105 and 115 of the inductors 1- Iu and 1-Id. The vernier windings 155 of amplifier Ad are so related to the other windings of this amplifier that an increase in the current flowing in this winding (155) increases the output current of the amplifier Adtthe vernier windings 145 of the amplifier Au are so related to the other windings that'a'n increase in the current flowing through this vernier winding decreases the output of amplifier Au. 1

The Control Unit includes the master switch MSl, which has a standby position labeled 0 and three each hoist and lower positions labeled 1, 2, 3. The switch MS1 controls the contactor 1M and a plurality of relays including, in addition to the relays REH, REL, ,RESl, RES2, RETZ an-dREB, the relays RET3,-REL1, REHl. The coils of the relays REH, REL, REHl and RELl, REL2, RET2, RESl and RES2 are supplied from conductors AL5 and AL6 through the selecting contacts 171 and 173 of the switch M81. The contactor 1M and the relay RET3 are supplied from conductors AL6 and AL13 through selecting contacts 175, 177, 179 of the relays REHI, REL2 and'RET3. The braking relay REB is similarly supplied from conductors AL6 and AL13.

The Control Unit also includes a rectifier RH for boosting during hoist and the weight responsive rectifier RW. The rectifier RH is supplied from conductors AL7 and 'AL10 through a contact 181 of relay REHl which is normally open. In addition, the output of rectifier RH is shunted by a normally closed contact 183 of relay REHl. Rectifier RH.or contact 183 is connected in series with rectifier RW and tachometer T in a circuit extending from the positive terminal of rectifier RW through rectifier RH or contact 183, one of the input windings 103 of induct-or 1-Iu, the input winding 113 of inductor 1-Id,the tachometer T to the negative terminal of rectifier R W. The effect of current flow through the rectifier RH is to enhance the effect of bias network B1 and to reduce the effect of bias network B2. Thus, when current flows through rectifier RH the impedance ;of inductor l-Iu .is decreased and the impedanceof inductor 1-Id is increased. Rectifier RH then tends to increase hoist torque and decrease lowering torque. RectifierRW has a similar effect, that is, the greater the load the more rectifier RW tends to increase the hoist torque and decrease the lowering torque. The output of rectifier RW is large compared with the output of tachom:

V eter T. ,The output of the latter, as indicated inFig. 213,

the conductor AL9. The other terminals of each set of output windings are connected to conductors L01 and L02, respectively, through rectifiers 161 and 163 and 171 and 173, one 161 or 171 poled to conduct positive tends to enhance the effect of rectifier RW when the hoistdrum DR is rotating in the lowering direction'and to reduce the effect or rectifier RW when the hoist drum is rotated in the hoisting direction.

Stand-by Figs. 2A-2B p In the stand-by condition of the apparatus, conductors L1, L2, L3 and L4 are energized. Conductors AL5 through AL13 are then energized, the latter so long as limit switches LS and'LK are closed. Amplifiers Au and Ad are then supplied with potential and networks B1 and.B2 are energized from the potential at conductors AL7 andLOland AL7 and'LO2.- Thus, the impedances 'low'e'riug torque with no load on the hook HQ.

The switch MSl is in the zero position and relay REHl'is deenergized so that there is no potential impressed through rectifierRH. Assuming that in standby there is no load on the hook, the potential impressed from rectifier RW is substantially zero and the hoist drum being at 'res'tthe potential from tachometerT is zero. Thus, the inductors 1-Iu and 1-Id remain set so that if they were energized the lowering torque would be from 30 to50%.

With the switch M51 in the zero position, relays REH, REHI, REL, REL1,-REL2, RES, RESL RES2, RET2 are deenergized. "Contactor 1M, relay RET3 and relay REB are then'deenergized. Thebrake B is then applied to theMotor and the resistance in the rotorcircuit of the motoris at a maximum. If at this time a load were applied to thehook HO, the tendency of the Motor to overhaul the load would be suppressed by the brake B.

Atthis timethe field winding TS is energized from the rectifier RF. The field is-at a maximum since contact 189 of relay RELI is closed. I

Assume first that alowering operation with no load on-the hook is to be carried out. Under such circumstances, the switch MSI is moved to lower position 1 and reIay RELZis energizedand at its now closed contact 1 77 supplies current from conductors AL13 and AL6 to energize contactor 1M. The latter closes its contacts 121, 123, 125, supplying power-to the Motor. ln addition, at another now closed contact 191 of relay REL2,'relay RET3 (analogous'to 'RETI of Figs. lA-lB) i is energized closing its contact 179 to lock in the motor independently of relay RELZ. At thispoint, current is supplied'to the input-windings'103 and 105 and 115 of the inductors from'the amplifiers Au and Adto'produce 30 to 50% lowering torque. The'output of the tachometer T tends to decrease this lowering-torque so'that the operation of the motor is stabilized at about 30 to 40% rated speed.

If higher speed is now desired, the switch M81 is moved to lower position 2,energizing relay RELl. The normally closedcontactliii which shunts out resistance 195 in the circuit of field'TS is now opened 'andthe excitation of the field is reduced so that the potential of tachometer T is reduced. The balancing potential of the tachometer is then reduced so that the lower torque is increased and the speed of the Motor is correspondingly increased. i A further speed increase is achieved by moving the switch M81 to lower position 3. "Inthis case, relay REL is actuated. This relay, at its contact127, disconnects the supply to bias network B1 and connects 'bia's network B2 to be'supplied between terminals AL7 "and AL12 through the variable resistor 136. In this way, the down torque is substantially increased. In addition, relays RESI and RETZ areactuated through'now closed contact 197 of relay REL and after relay RET2times out, relay RES2 is actuated through another contact 2010f relayREL. At contacts 203, 205, 207, 209, the. resistances 11, 15, 19-and 13,17, 21 in the rotorcircuit are shunted outin succession. Further, at a further contact 211 of relay REL the contactor 1M is locked in through the now closed contact 179 of relay RET3. The hook H is now lowered at the maximum speed.

it there is a load on the hook HO the rectifier RW supplies potential ineach of the lower positionsiof'the switch MS1 and this potentialttends to reduceithelowering torqueand increase thehoisting torque if there is a tendency to overhaul. In lower positions 1 'andl2 the torque-may beadjusted to theiprecise magnitude desired "by setting 'the resistors "RVl and RVZ in series with" the venierwindings and of the amplifiers Au' and'Ad. Now assume that the'hookHO with no load on it 'is' tobe raised. In this'case, switch M81 is moved to'hoist position 1. RelayREHl is then actuated. This'r'elay 'at'its lower-nowclosed contactcloses an energizing circuit 'for -relays'RET3 and REB. When relay REBis actuated, the-brake "B is released. When relay 'RET3 is actuated, it closes the contact 179, actuating contactor 1M. Power is now supplied through theeonductors L1, L2,.L3 and-L4 to the Motor.

Atanother now closed contact 181 of relay REH]. the rectifier RH is energized; in addition, the shunting contact 183 across the rectifier is opened. The rectifier RH now supplies current through the input windings 103 'andl113 of inductors 1'Iu and 1-Id, tending to increase the'hoisting torque and decrease the lowering torque. 'Theincrease is sufiicent to cause the motor 'to'raise'the'hook. Asthe motor raises the book, a counteracting potential is'suppliedfrom the tachometer T. 'This'potentialcauscs the speed at which the hook is raised to stabilizeat'about 30 to 40% rated speed.

If'higher speed is desired, theswitch MSl is set in hoist position 2. In this case, relay'REHis actuated. This relay, at its upper contact 133, disconnects'the input winding 115 of inductor 1-Id from the amplifier Ad and connects theinput windings 103 and 105 of'in'ductor l-Iu between conductors AL7 and.AL12through the variable resistor 136. The impedance ofinductorl-Iu is now substantially reduced and the Motor supplies increased hoisting torque. In addition, the lower normally open contact 221 of relay REH is closed, energizing'relay RESl. The'latter is actuated, shunting out a portionof the resistance (11, 15, 19) in'the rotor circuit. In addition, relay *RETZ is energized and it prepares a circuit through contact 223 for relay RES2. If still higher speed is desired, theswitch M51 is moved to hoist positionl3. At this point,'r'elay RES2 is energized through the contact 223 of relay RET2, further reducing the resistance in thecircuitof the rotor and thus increasing the hoist torque toia maximum.

When there is load onthe hook, the hoist torque is further increased by the potential supplied from the rectifier RW'which is supplied in series with RH.

The apparatus'shown in Figs. 3A and 313 includes a. Motor, a Hoist, anInductor Unit, a Vernier Unit and af Control Unit. This apparatus is supplied from conductors L1, L2, L3 and L4 'connectedin aduplexinterconnected three-phase system with transformer'4Z. The conductorsL1, L2, LS and L4 are energized through suitabledisconnectsS1, S2, S3. Potential-for the auxiliary components is supplied'fromconductors A114 and AL15, which :are 'co'nnected to the conductors LI and L2 througha :control' switch SW1, 1 and through auxiliary conductors 'AL16, -'AL17, .-AL13, A1419, which are'supplied fromsecondaries 5S1and15S2 of1trnnsformer'5Z. For convenience, the conductorsALZi) may alsobeconsidered-xas .a supply conductor. This conductor is connected to supply conductor AL18 through the overload and up limit switches LK. and LS.

The Motor-and the Hoist aresimilar to the. correspondingcomponents .insthe apparatus shown in FigslAand 1B, 2A:and 2B. TheInductor Unit issimilarto'thelnductor Unitin the apparatus shown in Figs. 2A and ZB-including inductors -1-Iu and :1-Id with input and output windings 103, 105, 113, 115 and 101 and Y111 similar to those-of thelatter. Theinput windings 103 and 105 of the inductors 1-Iu and thewvinding .115 of 1 1d are supplied front-biasing networks 1B1:.and 1B2. Th'ese'networksinclude rectifiers 1RB1 and '1RB2 supplied'from the V'ernier Unit.

Theoutput windings 101 and'lll are connectedin series between'opposite phase potential conductors L2 with the comutator and brush rigging omitted and the rotor winding insulated into two separate sections 311 and 313 spaced electrically by 90, that is, the inductor has two sections, the potential output of which is in quadrature. ,The stator of the Vernier inductor 1V1 is connected to the conductors AL14 and ALIS. One of the rotor sections 311, is connected to supply the network 1B1 through normally closed contacts 321 of the relay L in the Control Unit. The other rotor section 313 is connected to supply the network 132 through another normally closed contact 323 of the relay L, a normally closed contact 325 of the relay H of the control unit, and a variable resistor 327. The network IE2 is also adapted to be supplied from conductors AL16 and AL17 through a normally open contact 331 of relay L, contact 325 of relay H, and a variable resistor 333, a portion of the resistance of which may be shunted out by a normally open contact 335 of relay HQ It is seen that with relay L actuated, network IE1 is not energized and network 1B2 is energized from conductors AL16 and AL17. Under such circumstances, the down torque of the motor 14 5, and to be locked in through contact 363and its contact 367 in all hoist and lower positions. The exciting coillof the braking relay REB is adaptedto be connected be tween conductors AL18 and AL19 similarly to the coil I of relay TR. It is to be noted that when the switch M52 is reverted to stand-by, the brake is applied and at the I same time, while relay TR still remains actuated, power,

is applied to the Motor.

The relay H is adapted to be connected between conductors AL14 and AL1S in hoist positions 2, 3, 4, 5 through contact, 361 of relay MR which is closed inv normal operation, a normally closed contact 371 of relay L and contact 353. The coil of relay L' is adapted to be connected between conductors. AL14 and ALIS in lower position 5 through the contact 361, contact 355 and anormally closed contact 373 of relay H. Relay lTR is f adapted to be connected between conductors AL14 and ALIS in hoist positions 3, 4, 5 and lower position 5 throughthe contact 361 and contacts 355 and 357. The coil of contactor 1A is adapted to be connected through the contact 361, and-contacts3SS and 357 and contact- 377 of relay between conductors AL14 and ALIS in hoist positions 3, 4, 5 and lower position 5. The coil of relay 2TR is adapted to be connected between conductors AL14 and ALIS through the contact 361, contacts S and 357 and a contact 375 of relay lTR in prevails in the absence of any additional supply to the a input windings 103, 105 and 113 of the inductors 1411 and l-Id. With relay H actuated, networklBZis not energized and network IE1 is energized from Winding 311 of the inductor 1V1.

The relationship between the amplitude of the output of the two windings 311 and 313 of theinductor 1V1 is shown in Fig. 4 in which the amplitude of the voltage impressed is plotted vertically and the mechanical displacement in either direction from the central setting is plotted horizontally. The potential of the winding 313 impressed on IE2 is seen to be in quadrature with the potential impressed on 1B1. The three curves shown for the potential of winding 313 correspond to difierent loadings of the inductor 1V1. It is seen that in the absence of other potentials,-the Vernier Unit with the inductor 1VI in thezero setting tends to maintain the impedance of the inductor l-Id at a reduced magnitude.

Thus, in the absence of, other potentials, the Motor, if

The Control Unit includes, in addition to the contactor 2M and the relays H andL, time delay relays TR, 1TR

so, I

and 2TR, contactors 1A, 2A and 3A, and another reset relay MR. ,Relay TR is similar in function to relay RET of Figs. 1A-1B and relay'RET3 of Figs. 2A-2B.

The coil of the reset relay MR is connected between conductors AL14 and ALIS. through contact 353 and is thus normally actuated. When thus actuated this relay is locked in through one of its contacts 361. The coil of contactor 2M is adapted to -be connected between conductors AL20 and AL19 through a contact 363 of relay MR and contacts 349 or 351 in lower positions 1, 2, 3 and all hoist positions and between conductors AL18 and AL19 through another contact 365 of relay MR and contact 347 in lower position 5. The coil of relay 2M is also adapted to be energized from conductors AL20 and AL19 through a contact 367 of time delay relay TR. I

,The coil of the time delay relay TR is adapted to be connected between the conductors AL18 and AL19 hoist positions and through contact 365 in lower position 35. and the mechanical displacement of the rotor in degrees I hoist positions 4 and 5 and lower position 5. The coil of contactor 2A is adapted to be similarly connected. The coil of relay 3A is adapted to be connected between conductors AL14 and ALIS through the normally open contact 379 of relay 2TR, the contact 361 and contact 357 in hoist position 5. The Control Unit also includes a hoist boosting rectifier lRH which is energized from conductors AL16 and AL17 through resistor 333 and contact 341 in all hoist positions.

The weight responsive rectifier RW andthe tachometer T are adapted to be connected to the input. windings 113, 103 and 105 of the inductors 1-Id and -1-Iu through rectifier lRH. and contacts 345, 383 and 385 in zero position and in hoist position 1.

windings 103 and 10S through a normally open contact 381 of relay H.

windings 103, 105 and 113 through contacts 383, 385,

343 and 34S; in -lower position 2 a portion of the resistance of a resistor 391 is included in this circuit; in lower position 3 more resistance is included and in lower posi- I tions 4 and 5 the whole resistor 391 is included.

Contactor 1A has a pair ofcontacts 401 and 403 which short out a portion of the resistances 11, 15, 19 in the rotor circuit of the Motor and an additional contact 40S whichi shorts out the inductor l-Iu, When this contactor is actuated the inductor unit l-Iu is set for maximum up gtorque.

417, 421 in' the rotor'circuit.

Stand-byFigs. 3A-3B gized. In the stand-by condition, switch M82 is in the zero setting and the normally closed contacts 321, 323,

371, 383, 325, 373, 385 of relays L and H are closed. I Current is then supplied through the biasing networks 131 and "IE2 as represented in Fig.4. This current reduces theimpedance of inductor 1-Id and thus would cause the Motor to deliver a down torque if it were energized' The rectifier RW and the tachometer 'T are also connected to the input windings. 103, 105, 113 of the inductors 1 414 and 1 1d through contact 345 and rectifier vlRI-I and the-rectifier RW delivers a potential such that if the 1': ;Motor were energized the tendency to produce down a In the other hoist positions the rectifier lRH is connected directly across In lower position 1 rectifier RW and the tachometer T are connected in series with input Contact-ors 2A and 3A each have contacts 407, 409 and 411, 413 in the rotor circuit of the Motor which progressively reduce the resistances 13, 17, 21 and 413,

In the stand-by condition of the apparatus shown in Figs. 3A and 3B, disconnects S1, S2 and S3 are closed l as is also switch SW1. The Vernier Unit is then ,ener-.

torque potentials by the Vernier Unit would be reduced in accordance with the weight on the hook HO. In addition, reset relay MR is actuated and its normally open contacts 361, 363, 365 are closed so that the circuits through the contactors 2M, 1A, 2A, 3A, the relay TR and the relays H, L, 1TR, 2TR, and REB are adapted to be energized. But since the switch M82 is in the zero position, contactors 2M, 1A, 2A, 3A, relay TR and relays H, L, ITR and ZTR, are deenergized. The Motor is then deeuergized and the maximum resistance is connected to its rotor circuit.

Operation--Figs. SA-SB Assume now that there is no load on the hook HO and that it is desired to lower the hook. The switch M82 is then moved to lower position 1. The weight responsive rectifier RW and tachometer T are then connected in series with the input windings 103, 105, 113 of the inductors l-Iu and 1-Id independently of the rectifier RH, but with no load on the hook the output of the rectifier RW is substantially zero and with the motor at rest the output of the tachometer is substantially zero so that initially the torque of the Motor remains at its stand-by magnitude.

In lower position 1 the contactor 2M is actuated and its contacts 301, 303, 305 are closed so that power is supplied to the field of the Motor. In addition, relay TR is energized and contact 367 closed so that the contactor 2M is supplied from conductors AL and AL19 independently of the switch M82. In lower position 1 the relay REB is actuated and the brake B is released.

With the system as now set, the Motor is energized and exerts a torque in the lowering direction. As the Motor picks up speed, the tachometer increases the impedance of inductor l-Id and reduces the impedance of inductor 1-Iu, reducing the down torque so that the speed is stabilized at about to of rated speed. Adjustments may be made by setting the Vernier inductor 1V1 in a position to deliver the desired potential. As can be seen from Fig. 4, the movement of the rotor of this inductor in either direction reduces the current flow through the input winding 113 of inductor 1-Id and increases the current flow through the input windings 103 and 105 of inductor 1-Iu. Thus, the down torque may be reduced and the up torque increased.

If it is desired that the motor operate at a higher speed, the switch MS2 is moved to lower position 2. In this position, the resistance (391) in series with the rectifier RW and the tachometer T is increased so that the current from the tachometer T is reduced and the down speed becomes higher. To attain a still higher speed, the switch M82 is moved to lower position 3 in which the resistance (391) in series with the rectifier RW and the tachometer T is further increased. By moving the switch to lower position 4, a still further increase in the speed of the motor may be achieved in this way.

To attain the maximum speed, the switch is moved to lower position 5. In this position, the relay L is actuated, opening the connection between the input windings 103, 105, 113 of the inductors 1Iu and 1-Id and the rectifier RW and tachometer T. In addition, the winding 115 is connected to be supplied from conductors AL16 and AL17 and the Vernier 1VI is disconnected from networks 181 and 1132. The down torque is thus further in creased. The relay 1TR is also actuated. This causes actuation of the contactor 2A which reduces the resistance in the secondary circuit of the rotor. The motor now operates to the maximum speed to lower the hook. If there happens to be weight on the hook, it alfects the speed of the motor in lower positions 1, 2, 3 and 4. In lower position 5 the weight on the hook does not atfect the motor since relay L is actuated, but the switch MS2 is not set to this position in situations in which the weight on the. hook is excessive.

16 Now assume that it is desired to hoist the hook HO without load on it. Under such circumstances, the switch M82 is moved to hoist position 1. The rectifier lRI-I is then supplied through the variable resistor 333 in series with it, from conductors AL16 and AL17. Current is then supplied through the input windings of the inductors l-Iu and 1-Id from the rectifier RW, the tachometer, and the rectifier IRH. This current is initially supplied pri marily by the rectifier lRH and is sufiicient to produce an up torque. The setting of the switch MS2 in hoist position 1 also actuates contactor 2M and relay TR. Power is then supplied to the Motor and it is energized, raising the hook. When the motor rotates, the tachometer supplies a potential tending to counteract the effect of rectifier IRH. As a result, the torque is balanced so that the hook is raised at a speed of about 30 to 40% rated speed.

If a higher speed is desired, the switch M82 is moved to the hoist position 2. In this position, relay H is actuated. The actuation of relay H disconnects the inductor 1V1 from the biasing network 1B2. The tendency of the inductor l-Id to produce down torque is then further reduced. In addition, the rectifier lRH is connected across the input windings of inductor l-Iu directly and a portion of the resistance 333 in series with the conductors AL16 and AL17 which supply the rectifier lRH is reduced so that the current flow through the rectifier IRH is increased. This increases the up torque. Further, the rectifier RW and the tachometer T are disconnected from the input windings of the inductors 1-Id and 1-Iu and do not affect the motor. The motor now rotates at a speed determined by the rectifier 1RH. Additional speed over a relatively small range may be obtained by setting the vernier inductor 1V1 to a position in which the excitation of the input windings 103 and 105 of inductor l-Iu is increased.

To achieve a still higher speed, the switch M52 is moved to position 3. In this case, an energizing circuit is provided for'relay 1TR and contactor 1A, the latter through contact 377 of now closed relay H. When contactor 1A is actuated the resistance 11, 15, 19 in the rotor circuit is reduced and, in addition, the inductor l-Iu is shunted out. The up torque of the motoris now only limited by the resistance in the rotor circuit. This up torque may now be further reduced by movement of the switch MS2 to hoist position 4 in which case contactor 2A and relay 2TR are actuated. The motor speed is then further increased. The maximum speed may be achieved by setting switch M82 in position 5, in which case contactor 3A is actuated through the contacts of relay 2TR and reduces the rotor resistance to a minimum.

Conclusion I With the apparatus disclosed herein a full range of controllable torque may be obtained over a wide range of speeds, and particularly at low lowering speeds. This torque is obtained without resort to an artificial load, such as a load brake and without excessive input current to the Motor.

In carrying out this invention, certain compromises need be made. Thus, when the operation is at sub-syn chronous speeds under the control of the inductors Id and la or 1-Iu and 14d, resistance is connected to the rotor of the Meter". The magnitude of the ohmic component of this resistance sets the upper limit to which the current input to the Motor can rise, and for the purpose of limiting this current, it is desirable that the resistance be high. But the magnitude of this resistance also sets the upper limit to which the counter-torque can rise, and it is desirable that this torque be as high as practicable. This demands that the resistance be low. In the practice of this invention, it has been found that a satisfactory compromise is effected with a resistance which results in input current in the range of 100% to of rated current with 100% slip.

In the preferred practice of this invention, the inductors Id and la, or 1Id and I-Iu are saturable reactors. The impedance of such reactors may be varied overa wide rangeby varying the direct current flowing through the input windings. Saturable reactors are available for use in the practice of this invention in which the impedance may be varied from .66 ohm to 110 ohms, that is, over a range of about 160 to 1.

The apparatus disclosed herein is a form of closed loop regulator in which the difierence between the Motor torque and load torque is measured by measuring the speedof the Motor. in such a regulator, instability may result from the fact that the time response of the motor and its associated driving components may be smaller than that of the inductors Id and Ia, or 1-Id and 1-Iu. To avoid the difiiculties which may arise from this diffcrence, the variable torque which is under the control of the tachometer T and is thus responsive to the speed of the Motor is maintained small compared to the maximum. When the hook H is loaded, the weight responsive rectifier RW brings the Motor torque to a magnitude very close to the magnitude of the torque exerted by the load. The dilierence between these two torques is variable. In the practice of this invention, the inductors are strongly excited and operate with a low time lag; any speed response resulting from the variable torque thus has a higher time lag than the inductors. With no load on the hook, the tachometer T is in command because the output of the load rectifier RW is zero, but the torque in this case developed by the Motor is not enough in excess of the friction in the system to move the hook HO and its associated components at a higher speed than that corresponding to the response of the inductor.

Further, it is to be kept in mind that while the weight responsive device including rectifier RW has important advantages in the practice of this invention, there is apparatus in accordance with this invention in which this component is not present and the apparatus includes only a speed responsive component such as tachometer T.

Such apparatus is within the scope of this invention.

It is noted that in Figs. 1A and 1B and 2A and 2B the transformer lZ and the transformer SZ respectively, which supply the conductor L4, are energized in the standby condition of the apparatus when the contactors M and 1M are open. This is desirable in situations in which the transformer 12 or the transformer 52 is of the highly magnetizable type since in such situations the application of power to the transformers 12 or SZ result in a surge of current of substantial magnitude. ln'the modification shown in Figs. 1A and 1B and 2A and 2B, this surge is impressed when the power is first applied to conductors L1, L2 and L3 while contactors M orlM are stillopen and the current flow through the transformers 12 or SZ has reached a steady state when power is ultimately supplied to the Motor by the closing of contactors M or 1M. Thus the surge is not applied to the Motor.

While specific embodiments of this invention have been disclosed herein, many modifications thereof are feasible. This invention then is not to be restricted except insofar as is necessitated by the prior art. 1

I claim as my invention:

l. Apparatus for controlling the supply of power to a motor from a three-phase supply comprising, in combination, first inductor means including input Winding.

means and output winding means, second inductor means including input winding means and output winding means,

18 ing means of said first inductor means, means connecting said second network to said input winding means of said second inductormeans, a vernier inductor having a first set of output terminals and a second set of output terminals, the output of said second set being displaced in phase electrically by one quarter period with respect to the output of said first set, means for connecting said first set of terminals to said first network to energize said first network, and means for connecting said second set of terminals to said second network to energize said second network.

2. Apparatus for controlling the supply of power to a motor having a wound rotor and first, second and third stator terminals from a duplex interconnected three-phase source having first, second, third and fourth poles, said first and third and second and fourth poles being at opposite phase potentials, comprising, in combination, means' for connecting said first pole to said first terminal, means for connecting said second pole to said second terminal, first inductor means, second inductor means, means for connecting said first and second inductor means in series with said second and fourth poles, said first and second inductor means then having an electrical junction, means for connectingsaid third terminal to said junction, a contact for shunting said first inductor means, resistor means connected in circuit with said wound rotor, additional contact means for shunting at least a portion of said resistance means, and means common to said contact and said contact means for actuating both said contact and said contact means.

3. Apparatus for controlling the supply of power to a motor having a wound rotor from a three-phase supply comprising, in combination, first inductor means including input winding means and output winding means, second inductor means including input winding means and output winding means, means forconnecting said motor to said supply through said output winding means of said inductor means so that a decrease in the impedance of said first inductor means tends to cause said motor to rotate in one direction and a decrease in the impedance of said second inductor means tends to cause said motor to rotate in the opposite direction, a contact for shunting the output windings of said first inductor means, resistance means connected in circuit with said rotor, additional contact means for shunting'at least a portion of said resistance means, and means common to said contact and said contact means for actuating them.

4. A drive for a hoist comprising, in combination, a three-phase hoist motor, conductors adapted to supply power from a three-phase source, hoisting inductor means connected between said conductors and said motor to produce a hoisting torque onthe reduction of the impedance of said inductor means, lowering inductor means connected between said conductors and said motor and adapted to produce a lowering torque on reduction of the impedance of said lowering inductor means,vernier means connected to said hoisting inductor means and said lowering inductor means for determining the impedance of both said inductorlmeans in dependence upon the setting of said vernier means, said vernier means being set so as to tend to produce a lowering torque in the stand-by condition of the drive, power supply means, a master switch having successive hoist positions for progressively increasing the hoisting torque of said motor. means connected to said switch in one of its initial hoist positions for connecting said power supply meansin circuit with said vernier means and both said inductor means for controlling the impedance of said inductor means, said power supply means tending to decrease the impedance of said hoistmg inductor means and increase the impedance of said'lowering inductor means, and

' means connected to saidswitch in one of its advanced positions for disconnecting said vernier means and said power supply means from said lowering inductor means and connecting said powersupplymeaus only to said hoisting inductor means so as to decrease substantially the impedance of said hoisting inductor means.

5. A drive for a hoist comprising a, threerphase motor, conductors for deriving power from a three-phase source, hoisting torque inductor means connected between said conductors and said motor for increasing the hoisting torque by reduction of impedance of said inductor means, lowering torque inductor means connected between said motor and said conductors for increasing the lowering torque by. reduction of the impedance of said lowering torque inductor means, a master switch for controlling said motor having a plurality of successive hoist positions for setting the motor to operate at progressively higher hoisting torques, said hoist positions being designated herein as low torque and high torque positions, means connected to said switch in one of said low torque positions and to said lowering and hoisting inductor means for varying the impedance of said inductor means o Pr du ehoistin r e hin a; w ng and. conas r mea s. on t o a w tc n on of. s i high torque positions and to saidinductor means for shunting out said hoisting inductor-meanmthe said drive being characterized by, the fact that the motor isof the wound rotor type and by resistance connected in its rotor circuit, and by the further fact that the contactor means includes means for reducing saidresistance simultaneously with the short circuiting of the hoisting inductor.

6. A drive comprising in combination a motor, power supplymeans, an electrically actuable contactor having unactuated and actuated conditions and including contact means open in the unactuated condition of, said contactor and closed in the actuated condition of said contactor, control means for controlling the direction of rotation of said motor, means including said contact means for connecting said power supply means-in circuit with said control means and said motor whereby when said contactor is actuated power is supplied to said motor through said control means, a controller having a neutral position, a first position and-second position, means connected to said controller and said contactor for maintaining said contactor in said-unactuated condition in said neutral position and for maintaining saidcontactor in said actuated condition in said first and second' positions, means connected to said controller and said controlmeans for setting said control means to tendto causesaid motor to rotate in one direction insaid first position and to tend to cause said motor to rotate in said opposite directiontin said second position, and delay meansconnected to said controller andactuable in said firstand second positions tomaintain saidcontactor actuated for a predetermined time interval after said controller is moved from said first'or second position to said neutral position.

7. A drive comprising in combination-a motor, power supply means, an electricallyactuable contactor having unactuated and actuated conditions and including contact means open in the unactuated condition of said contactor and closed in the actuated condition of said contactor, control means for controlling said motor, means including said contact means for connecting said'power supply means in circuit with said control means and said motor whereby when said contactor is actuated power is supplied to said motor through-said control means, a-

controller having aneutralposition, a first position and second position, means connected tosaid controller and saidcontactor. for maintaining said-contactor in said unactuated condition in said; neutral position and for maintaining said contactor in said actuated condition in said first and second positions, meansconnected to said controller; and said control means 7 for setting said ntrol e n p ce ne m de iop at onof. sa drnotor insaid first position andanother mode -of; opera tion.of;said-motor in saidsecond; position, and delay e ns nnne tcdsto saidicontroll'e: and. actuahlein said fi n se ond positions to maintain said columns actuated for a predetermined, time interval after. said controller is moved from said first or second position to said neutral position.

d. Apparatus for controlling the supply of power to a motor from a three-phase supply comprising, in combination, first inductor means including input winding means and output winding means, second inductor means including input winding means and output winding means, means for connecting said motor to said supply through said output winding means of said inductor means so that a decrease, in the impedance oi said first inductor means tends to cause said motor to rotate in one direc-.

tion and a decrease in the impedance of said second inductor means tends to cause said motor to rotate in the opposite direction, a. first biasing network, a second biasing network, "neans connecting said first network to saidinput winding means of said first inductor means, means connecting said second network to said input winding means of said second inductor means, a Vernier inductor having a first set of output terminals and a second set of output terminals, the, output of said second set being displaced in phase electrically by substantially one quarter period with respect to;the, output of said first set, a controller having, a firstposition and a second position, means including said controller for connecting said first set of terminals to said first, network toencrgize said first network, means including said controller for connecting said second set of terminalsto, saidsecond network to energize said second network, said terminals of said Vernier inductor being connected to saidifirst. and second networks as aforesaid in saidfirst position of said controller and means connected tosaid-controlicr for disconnecting the first set of terminals from said first network in said sec-.

end position of said controller.

9. Apparatus for controlling the supply of power to a motor from a three-phase supply comprising, in combination, first inductor means including input winding means and output winding means, secondzinductor means including input winding means and outputwinding means, means for connecting said motor, tosaidsupply. through said output wiudingmcans of said inductor means so that a decrease in the impedance. of said first inductor meanstends to cause said, motor. torotatein one direction and a decrease in theirnpedance of saidsecond in ductor means tends to cause said motor to rotate; in the opposite direction, a first biasing network alsecond biasing network, means connecting said first network to said input winding means oi said. first inductor means, means connecting said second networkto. said input winding means of said second inductor means, .a Vernier inductor having a first set of output terminals and a second set of output terminals, the output of said second set being displaced in phaseelcctrically by substantially one quarter period with respect to the output of said first set. a controller having a first position and a second position. means including said controller for connecting said first set of terminals to said first network to energize said.

first network, means including said controller for connecting said second set of terminals to said second network to energizesaid second. network, additional potential supply means, said terminals of said Vernier inductor being connnected to said first and'second networks as aforesaid in said first position of said controller, and means connected to said controller in said second position thereof for disconnecting said'first and second 1 sets of terminals frornsaid first and second networks and'ior connecting said first network; to; said, additional potential supply means to be energized therefrom.

No references cited. 

